Impact of thermal ultrasound on enzyme inactivation and flavor improvement of sea cucumber hydrolysates.

In this study, the effects of the thermal ultrasonic enzyme inactivation process on flavor enhancement in sea cucumber hydrolysates (SCHs) and its impact on the inactivation of neutral proteases (NPs) were investigated. The body wall of the sea cucumber was enzymatically hydrolyzed with NPs. On the one hand, the structure of NPs subjected to different enzyme inactivation methods was analyzed using ζ-potential, particle size, and Fourier transform infrared (FT-IR) spectroscopy. On the other hand, the microstructure and flavor changes of SCHs were examined through scanning electron microscopy, E-nose, and gas chromatography-ion mobility spectrometry (GC-IMS). The results indicated that thermal ultrasound treatment at 60 °C could greatly affect the structure of NPs, thereby achieving enzyme inactivation. Furthermore, this treatment generated more pleasant flavor compounds, such as pentanal and (E)-2-nonenal. Hence, thermal ultrasound treatment could serve as an alternative process to traditional heat inactivation of enzymes for improving the flavor of SCHs.

Characteristics and antioxidant properties of Harpadon nehereus protein hydrolysate-xylose conjugates obtained from the Maillard reaction by ultrasound-assisted wet heating in a natural deep eutectic solvents system.

BACKGROUND: Harpadon nehereus is a high-protein marine fish. A valuable way to add value to H. nehereus is to convert it into protein hydrolysate. The Maillard reaction is an effective way to improve the functional properties of peptides and proteins, which are affected by many factors such as reactant concentration, water activity, pH, temperature, and heating time. However, the traditional Maillard reaction method is inefficient. The purpose of this study was therefore to explore the effect of the ultrasound-assisted wet heating method on the Maillard reaction of H. nehereus protein hydrolysate (HNPH) in a new-type green solvent - a natural hypereutectic solvent (NADES). RESULTS: Harpadon nehereus protein hydrolysate-xylose (Xy) conjugates were prepared via a Maillard reaction in a NADES system using an ultrasound-assisted wet heating method. The effects of different treatment conditions on the Maillard reaction were studied. The optimized glycation degree (DG) of HNPH-Xy conjugates was obtained with a water content of 10%, a reaction temperature of 80 °C, a reaction time of 35 min, and an ultrasonic power level of 300 W. Compared with HNPH, the structure of HNPH-Xy conjugates were significantly changed. Moreover, the functional properties and antioxidant activity of HNPH-Xy were all superior to the HNPH. CONCLUSIONS: An ultrasound-assisted wet-heating Maillard reaction between HNPH and Xy in the NADES system could be a promising way to improve the functional properties of HNPH. © 2023 Society of Chemical Industry.

Inhibitory effects of ultrasonic and rosmarinic acid on lipid oxidation and lipoxygenase in large yellow croaker during cold storage.

Lipid oxidation will lead to the deterioration of flavor, color and texture of aquatic products with high fatty acid content. The mechanism of ultrasound (US) combined with rosmarinic acid (RA) on lipid oxidation and endogenous enzyme activities of large yellow croaker during cold-storage (4 ℃) was investigated. The result showed that the US and RA have synergistic effects in delaying lipid oxidation and inhibiting endogenous lipase and lipoxygenase (LOX) activities related to oxidation. The inhibition of LOX activity by RA was dose-dependent, and US showed a negative effect on the inhibition of enzyme activity in the presence of low concentration RA. Moreover, RA changes the enzyme structure through static fluorescence quenching and interaction with enzyme molecules. Hydrogen bonding and hydrophobic interaction are the main interaction forces between RA and LOX. This study could provide basic mechanism of US treatment cooperating with polyphenols to inhibit lipid oxidation during food preservation.

Effect of tea polyphenols on sturgeon myofibrillar protein structure in the in vitro anti-glycation model mediated by low temperature vacuum heating.

The binding mechanism between tea polyphenols and sturgeon myofibrillar protein (SMP) in the early stage (0, 2, 4 min), middle stage (6, 10 min) and late stage (15 min) of low temperature vacuum heating (LTVH) in an in vitro anti-glycation model was investigated. The result indicated that the protein cross-linking during LTVH treatment were mainly induced by tea polyphenols. The loss rate of free arginine (Arg) and free lysine (Lys) of SMP at the late stage of LTVH treatment (15 min) was 73.95 % and 83.16 %, respectively. The hydrophobic force and disulfide bond were the main force between tea polyphenols and SMP in the middle and late stage of LTVH treatment. The benzene ring and phenolic hydroxyl group of tea polyphenols can interact with the amino acid residues of SMP, which was exothermic and entropy-increasing. This study provides new insights in the interaction mechanisms between tea polyphenols-protein during heat treatment process.

Vibration mill-assisted complex enzyme hydrolysis for flavoring of freeze-dried sea cucumber powder.

This study aims to analyze the flavor differences of freeze-dried sea cucumber powder, processed for different time intervals, under vibration mill-assisted complex enzyme hydrolysis using electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS). The results of principal component analysis by E-nose showed distinction among the four groups of freeze-dried sea cucumber powder (papain-neutral protease (PN) and flavorzyme-neutral protease (FN), processed for 60 and 80 min). The GC-IMS revealed 35 volatile compounds. Subsequently, based on the fingerprint and heat map results, the flavor differences among the samples were clearly distinguished. When compared to the other three groups, the 60-FN group exhibited a greater variety and quantity of volatile compounds such as octanal, heptanal, hexanal, (E, Z)-2,6-nonadienal, and nonanal. The 80-PN group exhibited high amounts of 2-propanone, ethylbenzene, ethyl acetate, and 2,5-dimethylpyrazine. In addition, the vibration mill technique was considered to be a mild enzyme-assisted method. PRACTICAL APPLICATIONS: This study found that different enzyme types and physical technology operation time can affect the different volatile flavor compounds of freeze-dried sea cucumber powder, which can be quickly and effectively be identified by E-nose and GC-IMS technology to improve the flavor and quality of the product, while facilitating the rapid adjustment and development of the industry. Meanwhile, the results of the study could provide a reference for the deep processing and flavor improvement of the sea cucumber industry and make an important contribution to the related literature. In addition, this could also promote the development and application of non-thermal processing technologies such as vibratory mill in the freeze-dried sea cucumber powder industry.